After failing to show a statistically significant effect for treating the psychotic features of psychotic depression in three individual clinical trials, Corcept Therapeutics (Nasdaq: CORT) finally found something that its drug candidate, Corlux, is good at: treating Cushing's syndrome.

Cushing's is a rare, complex disease with no current treatments, so the Food and Drug Administration allowed the company to run a trial without a control group and said Corlux had to show a 20% response rate to gain approval.

Corlux crushed that number.

In one measure of its effectiveness, 60% of the glucose-intolerant patients responded to the medication. In the group that had hypertension -- high blood pressure -- 43% of the patients responded.

Corcept plans to apply to the FDA in the first quarter of next year. It's in a race against Novartis (NYSE: NVS), which presented positive data for its Cushing's syndrome drug, SOM230, earlier this year.

Given the small number of patients who have Cushing's syndrome, Corcept plans to sell the drug itself inside the U.S. But it's looking for a partner outside the U.S. There are plenty of options for potential partners, given pharma's increased interest in orphan drugs.GlaxoSmithKline (NYSE: GSK) launched a new unit in February to treat rare diseases. And Pfizer (NYSE: PFE) has shown interest as well, having purchased FoldRx and licensed Protalix BioTherapeutics' (AMEX: PLX) Gaucher's disease drug.

It wouldn't surprise me if those talks turn toward an outright acquisition. Corcept doesn't have much of a pipeline beyond Corlux, and at a market cap of less than $300 million, a pharmaceutical company may be able to use synergies to its advantage and net more from Corlux than Corcept ever could.

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